(1) Field of the Invention
The present invention relates to a conveyor system utilizing a linear motor, and more particularly to a conveyor system comprising a conveyor cart having running wheels, a guide rail for movably supporting the conveyor cart, and a linear motor a primary coil and a secondary conductor for driving the conveyor cart.
(2) Description of the Prior Art
This type of conveyor system utilizing a linear motor is characterized by its ability to run the conveyor cart at high speed by means of a simple construction. This conveyor system utilizes the linear motor to provide a propelling force for the high speed running of the cart. For realizing a lightweight cart body or where relatively light articles are conveyed, the secondary conductor is mounted on the cart and the primary coil on the guide rail since this allows a simple cart body construction. Conversely, where a great propelling force is required for conveying heavy articles or where a high speed conveyance is desired, the primary coil is mounted on the cart and the secondary conductor on the guide rail.
For driving the cart by means of the linear motor, the smaller the space between the primary coil and the secondary conductor the greater propelling force is generated. The space between the primary coil and the secondary conductor is maintained by utilizing the construction wherein the conveyor cart is supported through its running wheels by the guide rail. FIG. 15 of the accompanying drawings shows an example where primary coil C is mounted on the conveyor cart or vehicle V and secondary conductor P mounted on the guide rail A. In this case the primary coil C and secondary conductor P are fixed to a vertical relative relationship by running wheels 1.
Existing conveyor systems utilizing the linear motor have unsatisfactory operability. In a positional relationship as shown in FIG. 15, for example, primary coil C or secondary conductor P mounted on the vehicle V is disposed over secondary conductor P or primary coil C mounted on the guide rail A. The primary coil and the secondary conductor usually are spaced from one another by 2 mm or less. However, the running wheels inevitably become worn with use of the conveyor system which results in reduced diameters of the running wheels and changes in the space between the primary coil and the secondary conductor. This would cause the trouble of the primary coil and the secondary conductor getting damaged through mutual contacts. It is therefore necessary to change the running wheels when appropriate. However, the changing of running wheels tends to be forgotten since their wear progresses only slowly. The running wheels left unchanged lead to the above-noted trouble impeding the working of the conveyor system.
Thus, the known conveyor systems utilizing the linear motor require the wear of the running wheels to be kept under observation. In this sense the known systems have room for improvement with respect to operability.